Regioselectively Trisilylated Hexopyranosides through Homogeneously Catalyzed Silane Alcoholysis

• Published in: Journal of the American Chemical Society 2005-12, Vol.127 (51), p.18085-18092
• Main Authors: Chung, Mee-Kyung, Schlaf, Marcel
• Format: Article
• Language: English
• Subjects: Catalysis; Chemical reactivity; Chemistry; Exact sciences and technology; Galactose - analogs & derivatives; Galactose - chemistry; Glycosides - chemical synthesis; Glycosides - chemistry; Hexoses - chemical synthesis; Hexoses - chemistry; Inositol - analogs & derivatives; Iridium - chemistry; Mannose - analogs & derivatives; Mannose - chemistry; Nanostructures - chemistry; Organic chemistry; Reactivity and mechanisms; Silanes - chemistry; Trimethylsilyl Compounds - chemical synthesis; Trimethylsilyl Compounds - chemistry
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/ja056283i

The iridium complex [Ir(COD)(PPh3)2]+SbF6 - reacts with tert-butyldimethylsilane in DMA to form [IrH2(Sol)2(PPh3)2]+SbF6 -, which is an active catalyst for the regioselective di- and trisilylation of a series of representative methyl hexopyranosides, β-1,6-anhydrohexopyranosides and 1,3,5-O-methylidene inositol. The corresponding 2,3,6- and 2,4,6-silylated glycosides are obtained in a separable mixture of 47−89% (2,3,6-isomers) and 9−25% (2,4,6-isomers) yield in a single-pot reaction. The 2,4-disilylated derivatives of mannosan, galactosan, and 1,3,5-O-methylidene inositol as well as persilylated levoglucosan are accessible in >85% yield by this method. The homogeneous nature of the catalysts is a prerequisite for the effective di-/trisilylation, as nanoparticle colloid catalysts generated in situ from Pd2(dba)3 (∼1.5 nm average particle size) or Ru2Cl5(MeCN)7 (∼0.65 nm average particle size) result in only low yields.